let hd = {
  "title": "后盾人",
  "url": "houdunren.com",
  "teacher": {
    "name": "向军大叔",
    age: 22
  }
}
console.log(JSON.stringify(hd)); 
//{"title":"后盾人","url":"houdunren.com","teacher":{"name":"向军大叔"}}

console.log(JSON.stringify(hd, ['title', 'teacher', 'name']))
console.log('-------------------------------------------\n')


var ret = JSON.stringify(hd, function(key, val) {
  console.log(key, val)
  if(key === 'age') {
    return val + 10;
  }
  return val
})
console.log('-------------------------------------------\n')

console.log(ret); 
//